Technical principle of top-coal caving with vibration and its practice

Low recovery ratio of top-coal in the fully-mechanized coal mining is a hot technical problem. A series of investigation methods and results of mechanical design, laboratory experiments, DEM numerical simulation, and in-situ practice of the vibration top-coal caving are described. The experimental results demonstrated that the vibration effect range can reach 0.65 m far from the roof of mining space; and it is also found that vibration frequency 1.0 Hz is the optimum choice. The numerical simulation results illustrated that the top coal could be caved layer by layer, with the effect of vertical weighty and horizontal vibration forces working together. Consequently, the waste stone ratio in mined coal was decreased and the recovery ratio of top coal was increased. The results of 6 months in-situ practice in Wangzhuang mine, Lu'an Coal Industry Company, demonstrated that the recovery ratio of top coal was increased by 3% in average with the vibration mechanism. The systematical investigations have demonstrated that the vibration top-coal caving is an advantageous and profitable technique, which can greatly increase the recovery of top-coal and decrease the waste stone ratio.